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Courses:
Organisms (BIO 114), Introduction to Biometrics (BIO 454/554), Marine
and Freshwater Invertebrates (BIO 409), Scientific
Perspectives (GSCI 104)
Research Interests: Chromatin diminution
during development of microcrustacea.
My laboratory is studying how genomic
reorganization is changing how we think about evolutionary
processes. Specifically, we are examining how genomes respond to
DNA loss and massive intragenomic reorganizations and whether the
highly repeated DNA sequences found in many organisms are functional or
"junk" DNA. Certain planktonic crustaceans (copepods) excise
major portions (35 — 95%) of their presomatic chromosomes during early
development in a highly precise and regulated manner, thus reducing the
size of their nuclear, somatic genome. This phenomenon is called
chromatin diminution. The somatic DNA contents of copepods vary widely
according to species (0.5 — 30 pg). Chromatin diminution may be a
mechanism that controlls genome size and accelerates rates of
speciation.
Our approach to understanding chromatin diminution
is best described as integrative. One of the hypotheses we are testing
is that genome size is correlated with development rates and body size,
traits that strongly influence the fitness of copepods and hence their
ecological and evolutionary success in nature. We sample species
broadly within an order of copepods and measure correlations between
genome size and fitness traits. This project involves field
collecting, laboratory culture, and histological preparations to
measure DNA contents. To adjust our computations of correlations
for phylogenetic relationships, we are using the tools of molecular
systematics to build a phylogeny. This tree also enables us to
trace the evolutionary origins and losses of chromatin
diminution. A third endeavor is to identify the heterochromatic
sequences that are excised and to construct a quantitative and
mechanistic model of DNA content before, during, and after the
chromatin diminution events. The integrative nature of this work
necessitates collaboration with colleagues around the world who have
expertise that complements that of my laboratory. Among our lab’s most
active collaborators are Ellen M. Rasch at James H. Quillen College of
Medicine, East Tennessee State University; Andrey Grishanin at the
Russian Academy of Sciences; Carlos da Rocha at University of Sao
Paulo; and Maria Holynska at the Polish Academy of Sciences.
Selected publications on chromatin diminution or evolution of genome
size: *student co-author
Rasch, E.M. and G. A. Wyngaard. 2008.
Heterochromatin endoreduplication prior to gametogenesis and chromatin
diminution during early embryogenesis in Mesocyclops edax (Copepoda:
Crustacea). Journal of Morphology, April issue.
Rasch, E.M. and G.A. Wyngaard 2008. Endopolyploidy in cyclopoid
copepods. Journal of Crustacean Biology 28(3): in press.
Rasch, E.M. and G. A. Wyngaard. Gonomery and chromatin diminution in Mesocyclops longisetus (Copepoda).
Journal of Crustacean Biology, in press.
Suarez-Morales, E., G. A. Wyngaard, M. A Gutierrez-Aguirre and J
Costanzo*. 2007. Life history traits of Mesocyclops thermocyclopoides
Harada, 1931 (Copepoda, Cyclopoida) with observations on naupliar
morphology. Crustaceana, 80(10): 1205-1222.
Grishanin, A.K., E.M. Rasch, S.I. Dodson, and G.A.
Wyngaard. 2006. Genetic architecture of the cryptic speices complex of Acanthocyclops vernalis (Crustacea:
Copepoda) II. Crossbreeding experiments, cytogenetics and a model of
chromosomal evolution. Evolution 60: 37-46.
Rasch, E.M. and G.A. Wyngaard. 2006. Genome sizes of cyclopoid copepods
(Crustacea): Evidence of evolutionary constraint. Biological Journal of
the Linnean Society 87: 625-635.
Rasch, E.M. and G.A. Wyngaard. 2006. Changes in nuclear morphology
associated with elevated DNA levels during gametogenesis in cyclopoid
copepod with chromatin diminution. Invertebrate Biology 125: 63-75.
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